The Dark Assassin
by Amari412
Summary: Heavily AU. Melinoe and Isabella have been trained nearly their whole lives for one thing and one thing only: The destruction of the Dark One. But in order to defeat him, Mel and Issy must travel back to the past where he isn't as powerful. Issy knows what she has to do, but will she have the strength to do it, and what would it really cost her?


**Prologue**

The two lone figures stood on opposite ends of the Training Field. Both women were tired, but the fire in their eyes hadn't faded, not yet. As long as there was still a spark left, they would fight. Just as they had been trained to. They carried no weapons, despite many available to them. All they had was their wits, physical prowess, and, of course, magic.

On the far right was the much younger girl. She was pale, but her skin was tinted slightly with a hint of gold. Her eyes were blue, and her gaze long like a hawk. Her red-brown hair was pulled back into a messy bun, clean off her slim neck. She wore a black training tunic with sleek matching leggings and black flat heeled combat boots. She was much smaller than her opponent, but the older girl, and all present, knew not to underestimate her. After all…she was the Dark One's daughter.

The girl on the far left was somewhat close to her age, but they were almost a year apart. She was taller, sleeker, had much more combat experience than her opponent. Her red hair was let wild, reminding all of a flame. Her eyes were a green-gray color, reminiscent of her mother, who was queen of the world she inhabited. In contrast to her opponent, but not fitting her abilities in the slightest, she wore a white training tunic with matching leggings and boots. She kept her head high and her stance strong like the princess she was. Princess of the Underworld.

On his throne, Hades watched them with interest. The king of the underworld and his fiery queen, Zelena, looked on at the two girls as they stood opposing, waiting like eager hounds for a command. Though they waited like hounds, they were sleek and strong like jungle or savannah cats. With a smirk, he finally gave it.

"Begin!"

The brunette was quicker to react and quickly shot blue-black lightning from her hands. The bolts hit the red haired princess, but she wasn't without magical resources of her own. She worked through her pain, allowing it to fuel her abilities. Green fire shot from her hands as she fell to the ground, writhing but determined to keep in the fight. This momentarily distracted the younger girl as she dodged away from the flames. The lightning ceased as flames engulfed the field. Temporarily blinded by smoke and unable to breathe just right, the brunette didn't see her opponent rush through the flames unharmed and take her down from behind.

The tackle sent the pair rolling and ended with the brunette on top. With a pained yell, the fire died away around them, forming into a ball in her hand. But the red head wasn't out just yet. Reaching a hand out, she used her fear this time to fuel her power. To the brunette's surprise, water flooded the field, seemingly out of the air. She jumped away, seeming to float just above the water, scanning for any sign of her opponent. The red head leaped out and took her down, both of them crashing into the water below.

Zelena looked on concerned. "Do you think we should stop them? It could get too intense…"  
"Don't worry they're fine" Hades took her hand, "They've trained all of their lives for this".  
"But this isn't their final exam now isn't it?"  
"No. To test their skills, they need better opponents than just each other".  
"You mean you're sending them out on a job?"  
"Not just _a_ job. _The_ job"  
"They're not ready. Even I know that".  
"They've trained all their lives. Trust me, my dear" he kissed her hand, "They're more than ready".  
"What if something happens to them?"  
"Then we all know the consequences".  
"And what? We have to be willing to take such a risk?"  
"We swore when we took Isabella in that we'd train her, both of them, for this. I know you love Issy like a daughter, but this was what she was born to do".  
"And Melinoe? If we lose our little girl?"

Hades gave a sad sigh and looked down. "I…I'll be devastated just the same as you. But it's a chance she's willing to take to help her friend. I trust our daughter, and so should you. They're good, both of them. It's time they fulfilled their destiny".

Zelena also let out a sad sigh. "Shall…shall I prep the spell then?"  
"If you could, darling, I'd appreciate it" he gave her another kiss to her hand and slowly let his wife slip away.

The king of the dead turned to water that now flooded most of the throne room. He shook his head as if looking at a mess children had just made.

"Isabella! Melinoe!" he called their names.

The two combatants emerged from their flood at the sound of their names. They landed gracefully, kneeling without batting an eyelash. Hades of course looked more than pleased.

"Rise, you two. Walk with me".

The pair looked at each other for a moment and then stood to follow him out. The redhead, Melinoe, smiled as they followed behind the man she called father. The brunette, Isabella, was a little more stoic about the whole thing. She had a knack for hiding her emotions even from those closest to her.

"You two have trained all your lives for this" Hades sighed a little and stopped in front of a door to look at them, "Look at you two…It seems like only yesterday this was just play to you girls. And now look. You're fierce, strong, everything a good assassin should be".  
"Thank you, father" Melinoe's smile, so like her mother's, didn't fade.  
"I expect great change from you both" he told them.  
"And you won't be disappointed. We will rescue her…and I will bring you the dagger…and his heart" Isabella promised.  
"Is the spell ready?" Melinoe asked.  
"Just about. The latest you two leave is tomorrow"

Zelena stepped foot out of the room and looked over at her husband, daughter and goddaughter. She looked concerned briefly, which caught the attention of Hades.

"Is everything alright love?"  
"Everything's fine. The spell's ready. I just wasn't expecting…you know…so soon-"  
"They won't be leaving yet. I'm giving them a day to say goodbye to their friends…and to us".  
"You think the entire timeline is going to change?"  
"I'm not saying it will, but it could".  
"So the butterfly effect applies?" Isabella wondered looking at her godparents with concern.  
"Yes…so no one can know who you two are or where you're from…not even us" Hades nodded.  
"But what if you catch on?"  
"Catch on? As in figure it out on our own? Well then you're not doing your job as an assassin. No one can know you're there. Remember, the Dark One can see the future, but with your jump, he won't be able to see a thing because nothing will be certain now. Now" he put his hands on the girl's shoulders, "You have twenty four hours to say goodbye to everyone. Tomorrow, at this time, you'll be going back in time…and hopefully saving us all".  
"Yes Lord Hades" they said together.

The Underworld king smiled. "Now, on your way"

The two bowed and went their own way. Zelena took his hand with a saddened worried look. Hades rubbed her hand with his thumb, making small circles to soothe his beloved.

"It'll be alright. They'll be fine. They've trained all their lives for this" he tried to reassure her.  
"What if…what if we don't meet?"  
"They won't be going that far back. We'll still know each other, if everything's set as it should be".  
"Still...they change one thing and everything changes".  
"The only thing that needs changing is Rumplestiltskin's living status…Isabella is more powerful than he is. If anyone can take him down, it's her. Have faith in the girls. They'll make it, and everything will be better. Just trust them".

Isabella and Melinoe had their own friends to talk to. When they reached the woods outside their home, they simply hugged and went their separate ways. They both had their own worries about this particular mission. After it, they'd probably not know each other as well.

"We've known the risks all our lives…We have to do this. To save everyone" Melinoe reassured her.  
"I know…I'll just miss you".  
"I'll miss you too. But you know, I think there's someone out there who will miss you far more" the underworld princess winked as the parted.  
"I know he will".  
"He loves you, I hope you know".  
"Again, I know but…he deserves someone better".  
"Does he?" another voice cut between them.

The girls turned and Melinoe smiled. The red head put a supportive hand on her friend's shoulder and disappeared with a snap of her fingers. Isabella rolled her eyes and turned to the interloper in question. She looked down shyly.

"Oh…hey, Vince" she smiled and kept her gaze down.  
"What was that?" the boy, Vincent, asked, trying to get her to look at him.

Vincent was a little closer to Melinoe's age than Issy's. In this shape, he technically could look however he wanted, as his kind were expert at such things. In this form, Vincent was a head taller than Isabella and fair skinned, though he was usually dirty from working in the stables and helping to maintain the Underworld's own zoo. He had a special way with animals, most notably reptiles, fish, and some birds. His hair was as dark as a raven's wing, wild and curly. His eyes however were the most beautiful feature of him, to Isabella at least. They were crystal blue and clear as day. They could change color depending on his mood, mostly to gold or brown. But for the time being, they kept their gentle blue. He wore his own black working robe and his knee high working boots were kept to a brilliant shine despite being around animals all day.

"I said hi" she finally looked at him and Isabella felt her face grow warm.

Vincent grinned. "Well hello to you too, Miss Isabella"  
"Can't you ever just call me just Isabella or Issy?"  
"Does everything have to be casual with you?"  
"Well, I'm not training, and we're not around the royals. Why not?"

Vincent cocked his head as if to say she had a point but quickly jumped to another subject. "Who deserves better?"  
"You do…You know I like you…a lot".

He looked disheartened. "Issy-"  
"Ha! Just called me by my nickname!"  
"Don't act like it's the first time, for goodness sake. You know why we…we can't".  
"I'm not afraid of you if that's what's got you doubting me".  
"Not just me. Isabella, we're on two different paths".  
"Really?" Issy leaned against a tree, "Or perhaps you're afraid of the one with the darkest magic running through her veins?"  
"Don't speak to me of darkness. You and I know very well I have cursed blood too".  
"But with you that's normal. You're…a dark denizen I guess".  
"Dark denizen?" Vincent chuckled, "Great use of alliteration. But it's not that exactly that bothers me".  
"Then what does?"  
"What you were brought here to do".

Isabella paused thoughtfully. Vincent had been against her training ever since he discovered the reason. It was what made him give up on becoming an assassin himself. That, and his passion for animals. He didn't want his friend to become a killer to change the fate of everyone. The whole world shouldn't be on her shoulders and Vincent pitied the girl all the more for it. He was brought out of his thoughts by Issy's sigh.

"You know why I have to do it. I have to save her…she's my mother for goodness sake".  
"I know, but why not rescue her here, in this time?"  
"He's too strong for me right now".  
"No he isn't" Vincent gave her a serious look, his eyes slowly turning a shade of light gold, "You're stronger than him…you were born stronger than him".  
"You still believe that".  
"I'll never stop believing it".

She stood again and put a hand to his cold cheek. "We're using the spell tomorrow".  
"WHAT?!" he pulled away, his eyes going gold and his pupils slitting, "Tomorrow?! What the hell is Hades thinking?!" Vincent hissed.

Isabella looked a little saddened as Vince turned and calmed himself. She kept her gaze down again.

"He…he believes in us. He thinks we can do this. Me and Melinoe".  
"Well he's mistaken. I swear, he's setting you both up for failure".  
"Vincent-"  
"NO!" he turned and Issy jumped back a little out of reflex rather than fear.

His teeth had elongated into slim points that stuck out even when his mouth was closed. His tongue, forked, flicked and waved. She held a hand out, unwavering and unafraid.

"Vincent…calm down, please" Issy kept her eyes on him, though she had to look up in attempts to stare down his half beast self.  
"Go!" he hissed and fell to the ground writhing in pain.  
"No! I won't leave you!" she went to the ground with him, watching helplessly as his glamour started to fall apart, melting off of him like ice in the heat.

Under the glamour she saw the shining green scales of his face, his real face. She hadn't seen him like this in a long time, not for the past six months since he had an episode like this. Isabella put his head in her lap and ran a hand over his melting cheek soothingly, hoping it would pass soon. Vincent shook, trying to literally pull himself back together, trying to murmur his spell in between bouts of shaking and hissing.

"Shhh…it's okay Vince…I'm here. I'm here. It's okay. Just let it happen. Let it flow…it's okay"

His head snapped up and he almost bit her. But Issy was smart and knew how to handle that by simply bopping him on the nose. This forced his head away and sent him back to shaking and practically cowering. Despite it all, Issy stayed with him, waiting for the pain and anger to pass. He was left shaken, as he always was whenever he had episodes like this. She just held him as he regained his composure and was able to piece his glamour back together again. Issy stroked his dark hair and kept her calm demeanor. Finally, his glamour pieced itself back together.

"Better?" she asked.

Vincent let out a pained, sad moan. "Hardly…but better than that I suppose".  
"I'm sorry…but it's what needs to be done".

He got up and took her hands, pulling her up with him. Vincent struggled just a little but with her help was able to keep his balance. Issy's eyes found his and she could see his disapproval.

"Don't do this…please. Stay here, with me. If you go, we'll lose everything we love. We'll lose each other".

She reached a hand up and caressed his face. Issy wanted to stay in that moment. She wanted to just run away and forget everything. But her family needed her first and their needs outweighed her wants.

"No matter what happens, Vincent…I promise I will always, always, find you".

 **Author's note: Yay for firsts! This is my first OUAT fanfic, and it's going be straying far from the show, as you can clearly see. Lots of OCs are going to be introduced, and no, I'm not following the show anymore, as I actually fell out with it a couple of seasons ago (The Frozen Storyline killed it in my honest opinion). But I wanted to see if I could do something a little original with the things I do know. As you can tell this is also clearly AU. Hades didn't die, Zelena did reform him so he is kinda a good guy. Robin Hood is still alive, and his daughter is raised by Zelena and Hades. Everyone's alive, I'm not doing the whole Jekyll and Hyde BS (Though it is very tempting cause I adore Sam Witwer). So yeah, everyone's kinda living somewhat normal lives in past Storybrooke. Anyway, please leave a review below I'd greatly appreciate it.**

 **Next chapter: Issy and Melinoe arrive in past Storybrooke, arousing the suspicion of the key players. Meanwhile, Vincent goes to see another friend about an enchanted item that may be able to help him keep his animalistic side at bay.**


End file.
